1. Field of the Invention
This invention relates to a data processing apparatus and a data processing method, and more particularly relates to a data processing apparatus, a data processing method, and a recording medium that are capable of receiving and recording the transport stream, for example, broadcasted as a digital satellite broadcast program and reproducing the recorded transport steam normally.
2. Description of Related Art
Recently, the digital satellite broadcast according to the transport stream has been started practically, and various digital satellite broadcast receiving apparatus have been commercialized. In such digital satellite broadcast receiving apparatus, a packet that constitutes the received transport stream is stored in an FIFO (First In First Out) memory temporarily, and then supplied to AV (Audio Visual) decoder successively. In the AV decoder, the data loaded on the packet is MPEG (Moving Picture Experts Group)2-decoded, and as the result a picture and sound are generated.
Herein, the AV decoder is provided with, for example, a built-in PLL (Phase Lock Loop), the PLL generates the system clock from 27 MHz clock to thereby decode the packet.
In detail, some packets that constitute the transport packet include PCR (Program Clock Reference) for calibrating the system clock, PTS (Presentation Time Stamp) for representing the display time, and DTS (Decoding Time Stamp) for representing the decoding time. The built-in PLL of the AV decoder calibrates 27 MHz clock according to PCR, and generates the system clock. The AV decoder performs the processing so that the packet is decoded and the picture and sound obtained from the decoding are generated when the system clock is coincident with the time of DTS and PTS respectively.
However, the digital satellite broadcast receiving apparatus having a built-in device such as hard disk or the like for recording a digital satellite broadcast program has not been commercialized yet. In the case such digital satellite broadcast receiving apparatus is realized, it is impossible to calibrate 27 MHz clock by use of PCR included in the transport stream read out from the hard disk because the time interval between adjacent packets that constitute the transport stream broadcasted as a digital satellite broadcast program is not coincident generally with the time interval between adjacent packets generated when the transport stream that has been recorded in the hard disk is read out from the hard disk. As the result, it is required for the PLL of the AV decoder to generate the clock obtained by so-called oscillation by free running (referred to as free-run clock hereinafter).
In this case, because the AV decoder performs processing synchronously with the free-run clock, the free-run clock should be adjusted so as to be coincident with the frequency of the system clock obtained by use of PCR included in the transmitted transport stream in order to perform normal decoding in the AV decoder. Furthermore, it is required to control the reading of the packet recorded in the hard disk based on the accumulation quantity of the packet in the FIFO memory so that the FIFO memory located on the front end of the AV decoder will not overflow or underflow.
However, in the case that the frequency of the free-run clock cannot be adjusted within the guaranteed range in relation to, for example, the allowable deviation of picture color frequency, it is expected that the normal color is not displayed. Furthermore, in the case that the free-run clock cannot be adjusted so as to be coincident with the frequency of the system clock obtained by use of PCR included in the transmitted transport stream, for example, it is expected that the sound is not generated.
Furthermore, some IC (Integrated Circuit) having the AV decoder for performing decoding of the transport stream could not control the frequency of the free-run clock.
Furthermore, in the case that reading out of the packet recorded in the hard disk is controlled based on the accumulation quantity of the packet in the FIFO memory located on the front end of the AV decoder, a built-in CPU of the digital satellite broadcast receiving apparatus controls the reading. However, if the processing capacity of the CPU is low, it is difficult for the CPU to control the reading out of the packet from the hard disk.
The present invention has been accomplished in view of such problem, and the present invention provides an apparatus and a method that are capable of, for example, receiving and recording the transport stream, and reproducing the recorded transport stream normally.
A data processing apparatus is characterized by comprising a clock generation means for generating an independent clock that is independent of the system clock, a time stamp generation means for generating a time stamp based on the independent clock, an adding means for adding the time stamp to the packet that constitutes the received stream, a first output means for supplying a packet to which the time stamp is added to a recording apparatus, and a second output means for supplying the packet reproduced from the recording apparatus based on the time stamp added to the packet.
The data processing apparatus further comprises a recording apparatus.
The stream may be a transport stream.
The second output means may supply the packet reproduced from the recording apparatus to the processing apparatus or supply to the processing apparatus under the control performed by means of the processing apparatus.
A data processing method is characterized by comprising a clock generation step of generating the independent clock that is independent of the system clock, a time stamp generation step of generating a time stamp based on the independent clock, an adding step of adding the time stamp to the packet that constitutes the received stream, a first output step of supplying a packet to which the time stamp is added to a recording apparatus, and a second output step of supplying the packet reproduced from the recording apparatus based on the time stamp added to the packet.
A recording medium is characterized by having a program including a clock generation step of generating the independent clock that is independent of the system clock, a time stamp generation step of generating a time stamp based on the independent clock, an adding step of adding the time stamp to the packet that constitutes the received stream, a first output step of supplying a packet to which the time stamp is added to a recording apparatus, and a second output step of supplying the packet reproduced from the recording apparatus to a processing apparatus for processing the packet based on the time stamp added to the packet.
In the data processing apparatus, data processing method, and recording medium of the present invention, an independent clock that is independent of the system clock is generated and a time stamp is generated based on the independent clock. The time stamp is added to a packet that constitutes a received stream, and the packet having the added time stamp is supplied to a recording apparatus. On the other hand, a packet reproduced from the recording apparatus is supplied to the processing apparatus for processing a packet based on the time stamp added to the packet.
Therefore, the processing apparatus can process the packet reproduced from the recording apparatus in the same manner as used to process the packet that constitutes the received stream.